Sealed spark plug assembly



Al1g 12, 1952 w. A. BYCHINSKY SEALED SPARK PLUG ASSEMBLY Filed April lO, 1948 Patented Aug. 12, 1952 SEALED SPARK PLUG ASSEMBLY Wilfred A. Bychinsky, Flint, Mich/ assignorf to.l General Motors Corporationr Detroit, Mich., a

corporation of Delaware Application April 10, 1948-, Serial No. 20,273

8 Claims.

The, invention relates to spark plugs and ignition cablev connections thereto, particularly of, the waterproof type.

vThe invention has especially advantageous application to spark plugs and ignition cables which are enclosed in metal shielding to prevent interference with nearby radio reception. Shielded spark plugsnow in most common use comprise an insulation lined metal barrel which extends upwardly from thebase of the plug proper and forms a socket into which the end of the ignition cable. is intruded tov make contact withthe centralelectrode of the plug. The portion of the ignition. cable extending into the socket is generally enclosed in two or more removable sleeves of insulating material, one of which is of rigid construction and carries a metal tip piece including a short helical spring connected to the end of the ignition conductor,y and another of rubber or'similar material has an integral collar extending outwardlyY therefrom which serves as a packingv at the joint between the end of the plug barrel and thel abutting external flange on the end of the cable shielding conduit outside the plug. A coupling nut, having an internal ilange interlocked with the conduit external angeand threadedly engaging the plug barrel, secures the parts together.

Diiculty hasbeen encountered in such prior constructions, both with respect to preventing the entrance of moisture into the cable socket of the spark plug, and in obtaining the very high electrical continuity between the spark plug barrel and cable conduit which is necessary for proper4 radio shielding. After a relatively short period` of operation the rubber tends' toilow and lose its resiliency, allowing moisture to seep in from the outside between the two abutting shielding members, and from the interior of the cable'conduit between the cable and the rubber sleeve. Slight irregularities in the abutting sur faces. of the plug barrel and cable conduit, re-

sulting from either damage, warping or original poor machining', destroy the near-perfect mating contact necessary for satisfactory shielding; and

while the coupling nut serves as an additional electrical path forv the shielding currents, its use as` such is only partially effective and is not reliable.

Itis therefore an object of thisr invention to provide. a spark plug and ignition cable lead-in assembly incorporating improvedr means. for sealing against the entrance of moisture into the plug.

A further. object is to provide` such. anpasscmbly 2 particularly adapted. for radio shielded: ignition systems.

Other objects and advantages will becomeevident from reading the following descriptionVtogether with the drawing which showsialongitudinal section through?. a radio shielded aircraft spark plug and cable lead-in assembly. embody-- ing the invention.

In the drawing, the spark plug assembly indicated. generally bythe numeral i` comprises ak metal. body or base. portionV 2, externally vthreaded at 3' for securement in an engine cylinder head (not shown), an insulating body 4 having an upwardly open cylindrical recess serving as a cable sockety 5 at its upper end, a cylindrical metal shielding barrel ory shell 6 extending from the baseY portion 2 above the upper end of the insulating' body', and a central electrode 'I extending through the lower part of the insulating body and terminating at its upper end in the bottom of the; cable. socket 5.. The electrode 'l may be of' any suitable construction-that shown being providedfwith an auxiliary spark gap 8' for purposes incidental to the instant invention.

The; upper end of the spark plug shielding barrel 6 is provided with an internal ilange 9 which' extends over the upper end I0 of the insulatingl body'd and denes an opening II into the sparkplug. in alignment with the socket 5. An arcuate shaped gasket seat I2 is provided on the upper face of the iiange 9, for a purpose to be hereinafter. explained.

The ignition cable lead-in assembly indicated generally by the numeral I3 comprises an outer metal conduit I4, which may be in the form of" the spark plug end thereof into the socket 5 of the spark plug. The ignition conducting wire I-9; withinY the cable I8 extends a short distance beyond the end of the insulating covering 20 thereon, into the upper end of a metal terminal membersuch as the eyelet ZI to which is secured acontactV piece such as the coil spring 21 which resiliently bears against the upper end of the spark plug central electrode '1. For ease of assembly, the eyelet 2I is preferably provided with a U:shaped` socket 22 in its upper end into which the endzof the Wire can be inserted and the upper portionV of.` the eyelet then clinched around theV same.

Encircling the cable I8 between the gasket seat I2 on the spark plug barrel 6 and the conduit ferrule I is an annular gasket or packing member 23, preferably made of spring steel for maximum resilience and good electrical conductivity. The lower annular portion of the packing member 23 is generally C-shaped in radial section as shown, and conforms with the curvature of the seat I2 and the flat bottom face of the flange I'I on the ferrule I5. Extending upwardly from the C-shaped section of the packing member 23, and integral therewith, is a short sleeve-like section 24 which is of somewhat larger internal diameter than the diameter of the cable IS'and has an internal flange 25 at its upper end which provides a sufficiently restricted passage for the cable as to firmly grip and effect a depression of the insulation 20. n

Surrounding the portion of the cable extending into the spark plug is a resilient fluid-impervious sleeve 26 of soft rubber or like material',

having an integral enlargement 23 shaped to conform with internal surface of the C-shaped section of the packing member 23. The sleeve 26 including its enlargement 28 is permanently bonded to the cable insulation 20, eyelet 2I and packing member 23, and is preferably formed by molding the rubber directly around the cable with the eyelet and packing member in place and using the internal flange 25 at the upper end of the packing member as a dam atthat end.

In operation, with the coupling nut I6 tightcned-securely on the spark plug barrel 6, the C-shaped section of the packing member 23 is compressed between the flanges 9 and II on the conduit ferrule and spark plug barrel respectively, and by reason of its resiliency conforms sufiiciently closely to the surface of each such flange as to effect both a moisture proof seal and continuous electrical bond therewith. On account of the rubber sleeve 26 being permanently bonded to the cable'insulation and to the inner surface of the packing member 23, any moisture present within the conduit I4 or ferrule I5 is positively prevented from seeping into the spark plug, even should the rubber lose its resiliency after continued use. Further, by reason of the packing member 23 being made of spring steel or equivalent metal, it does not lose any appreciable amountv of resilience with age. y

I have'thus provided a spark plug and ignition cable lead-in assembly incorporating not only a more effective and longer lasting seal against entrance of moisture into the spark plug, but also a more reliable electrical bond between the interconnected radio shielding sections of the spark plug and cable conduit.

l. An ignition lead-in assembly adapted to cooperate with the socket-forming outer vcasing of a spark plug and the radio shielding conduit on the lead in effecting a waterproof joint therebetween, comprising an ignition conductor having an insulating covering, an electrically conductive eyelet member secured to one end of the conductor, an annular spring metal packing member encircling the insulating covering of the conducto-r and including an outwardly-closed elastically deformable C-shaped section, and a fluid-impervious sleeve of soft rubber or like elastically yieldable material surrounding the portion of the'conductor between the eyelet member and the packing member and permanently bonded to the insulation covering and to each of said members. f

2. An ignition lead-in assembly adapted to cooperate with the radio shielding shell of a spark plug and the radio shielding conduit on the lead in effecting a waterproof and electrically continuous shielding joint therebetween, comprising an elastically deformable metal gasket comprising an annular substantially flat portion having its outer extremities incurved to provide an outwardly convex portion, an insulated ignition conductor extending through the gasket and provided with a terminal member secured to the end thereof nearest the convex portion of the gasket, and afluid impervious sleeve of soft rubber or like material permanently bonded to the terminal member and to the conductor insulation and having an integral enlargement permanently bonded to the inner surface of the gasket.

3. In a radio shielded spark plug and ignition lead connector assembly, a spark plug shielding barrel having an arcuately recessed gasket seating surface on its outer end face, an ignition conductor with an insulating covering thereon extending into the barrel and having a terminal carrying member electrically connected to its intruded end, a metal conduit surrounding the insulation on the conductor outside the .barrel and provided with a substantially fiat gasket seating surface opposite the outer end face of the barrel, a spring metal C-section gasket encircling the cable between and resiliently pressing against said seating surfaces, a fluid-impervious resilient sleeve having its inner surface permanently bonded to the conductor insulation and its external surface permanently bonded to and substantially filling the C-section of said gasket, and means for coupling the barrel and conduit together so as to compress the gasket therebetween.

4. An electrically vcontinuous and waterproof4 joint between a spark plug radio shielding barrel and an ignition cable shielding conduit, comprising an internal flange at the upper end of the barrel provided with an inwardly and upwardly facing arcuate depression around the extremities thereof, a metal ferrule forming a continuation of the ignition cable shielding conduit and having a substantially flat extern-al flange disposed opposite the internal flange on the spark plug, a coupling nut securing the cable conduit to the spark plug barrel, an annular metal packing member of spring steel having a cylindrical section internally flanged at its upper end to engage the insulation on the cable and an expanded internal-annulus-forming section at its lower end, the last named section consisting of a flat portion resiliently pressing -against the external flange on the conduit ferrule and an arcuate portion resiliently pressing against the arcuate depression in the internal flange on the spark plug barrel, the internal surfaces of the packing member being permanently bonded to the cable insulation.

5. In combination, a radio shielding spark plug shell, a radio shielding lead-in conduit, an elastically deformable gasket of spring steel or the like having an annular portion of outwardly convex shape, oppositely disposed gasket seating surfaces on the spark plug shielding shell and lead-in shielding conduit, one of said seating surfaces being concave to receive and closely conform with said convex portion of the gasket, an insulated ignition conductor extending through the gasket, and a fluid impervious sleeve of soft rubber or like material permanently bonded'to both the inner conductor insulation `and to the inner surface of said gasket `convex portion.

6. An ignition lead-in assembly adapted to cooperate with the radio shielding shell of a spa-rk plug and the radio shielding conduit on the lead in effecting a waterproof and electrically continuous shielding joint therebetween, comprising an elastically deformable metal gasket comprising an annular substantially at portion having its outer extremities incurved to provide an outwardly convex portion, an insulated ignition conductor extending through the gasket, and a fluid impervious sleeve of soft rubber or like material permanently bonded to the conductor insulation and having an integral enlargement permanently bonded to the inner surface of the gasket.

7. An electrically continuous and waterproof joint between `a spark plug radio shielding barrel and an ignition cable shielding conduit, comprising an internal flange at the upper end of' the barrel provided with an inwardly and upwardly facing arcuate depress-ion around the inner extremities thereof, a metal ferrule forming a continuation of the ignition cable shielding conduit and having a substantially fiat external flange disposed opposite the internal ange on the spark plug, a cou-L pling nut securing the cable conduit to the spark plug barrel, an insulated ignition cable in said conduit extending into said barrel, an annular metal packing member of spring steel having a cylindrical section internally Banged at its upper end to engage the insulation on the cable and an expanded internal-annulus-forming section at its lower end, the last named section consisting of a nat portion resiliently pressing against the external flange on the conduit ferrule and an arcuate portion resiliently pressing against the arcuate depression in the internal flange of the spark plug barrel, the internal surfaces of the packing member being permanently bonded to the cable insulation.

8. An electrically continuous and Waterproof joint between a spark plug radio shielding barrel and an ignition cable shielding conduit, comprising an internal fiange at the upper end of the barrel provided with an inwardly and upwardly facing arcuate depression around the inner extremities thereof, a metal ferrule forming a continuation of the ignition cable shielding conduit and having a substantially flat external flange disposed opposite the internal flange on the spark plug, a coupling nut securing the cable conduit to the spark plug barrel, an insulated ignition cable in said conduit extending into said barrel, an annular metal packing member of spring steel having an expanded internal-annulus-forming section with a flat portion resiliently pressing against the external ange on the conduit ferrule and an arcuate portion resiliently pressing against the arcuate depression in the internal nange on the spark plug barrel, the internal surfaces of the packing member being permanently bonded to the cable insulation.

WILFRED A. BYCHINSKY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,321,782 Von Mertens June 15, 1943 2,402,049 Ingalls June 11, 1946 2,405,881 Frei Aug. 13, 1946 2,442,015 Peters May 25, 1948 FOREIGN PATENTS Number Country Date 216,046 Switzerland July 31, 1944 

